1. Field of the Invention
The present invention relates to power supplies. More particularly, the present invention relates to a method and apparatus of extending the supply of reserved power during a line power interruption.
2. Description of the Related Art
Over the past few decades, commercial aircraft has become a necessary mode of travel for personal and business reasons. To improve passenger comfort, commercial aircraft typically offer a number of entertainment activities that can be enjoyed by the passenger, such as video games, movies and various selections of music. In addition, various electronic systems for supporting communications and/or other in-flight functions are provided.
Such electronic systems typically comprise seat electronic units which receive in-flight entertainment programs from a central system and which subsequently deliver these programs to one or more passengers on the aircraft. These electronic units typically include circuitry which draw power from two different power sources, such as a +5 V power supply and a +3.3 V power supply. The +5V and +3.3V power supplies in turn obtain power from a 115V AC source via an AC-to-DC converter.
During a line power interruption or power suspension to the +5V and the +3.3V power supplies, reserved power is typically made available to the circuitry in the electronic units for a minimum period of time (typically 200 ms). This is typically accomplished by storing sufficient energy in holding capacitors that are coupled to the DC regulator, which is in turn coupled to the +5V and the +3.3V power supplies, to provide the supply current and voltage requirements of the circuitry in the electronic units.
In such a conventional system, the amount of time that power is provided to the circuitry, is dependent on the energy stored in the holding capacitors. The amount of energy stored may be increased, and the holding period may be extended, by increasing the storage capacity of the holding capacitors. This is accomplished by using larger holding capacitors, which results in a corresponding increase in circuit board space, weight and cost. By extending the holding period, the amount of current and voltage provided by reserved power may be extended, thereby ensuring that the circuitry in the electronic units is more reliable.
Accordingly, there is a need in the technology for an apparatus and method for extending the supply of reserved power to circuits during a line power interruption, without the need for increasing the size of holding capacitors coupled to the power source.